At the present time, N-acylated derivatives of mixtures of amino acids obtained by hydrolysis of proteins of animal origin are currently employed for cosmetic purposes.
Because of the their amphiphilic structure, these polyacylated lipoamino acids can progress rapidly through the first cell layers either to restore deficient structures or to release their active ingredients within the epidermis.
Hence these lipoamino acid structures are particularly useful biological vectors as skin physiology regulators and prove to be appropriate for multiple applications, particularly in cosmetics.
The sources of these amino acid mixtures are today essentially collagen, elastin, keratin, and casein.
In view of their animal origin, these hydrolysates unfortunately have potential risks of contamination by pathogens which it would be desirable to avoid; users tend with increasing frequency to avoid animal-derived compounds for any application intended for human beings.
Moreover, British Patent No. 1,153,408 describes N-acylated derivatives of mixtures of amino acids obtained by hydrolysis of proteins of plant origin. However, the precise nature of these proteins is not described. Moreover, the present inventors have been able to ascertain that depending on the nature of the plant from which the protein is derived, the resulting compounds can have very different properties. They thus observed that N-acylated derivatives of mixtures of amino acids from hydrolysates of leguminous proteins such as soy had certain disadvantages.
Thus, solutions of such N-acylated derivatives, particularly solutions of salts of these derivatives, have relatively substantial coloration, which is troublesome in certain applications, particularly in the field of cosmetics. Moreover it is often necessary to locate the pH of cosmetic compositions at approximately 5.5, namely at a pH approximately that of the skin, to decrease their aggressiveness to the skin. Now the inventors have ascertained that solutions containing such N-acylated derivatives of leguminous proteins such as soy become cloudy as soon as their pH drops lower than approximately 6.8. Yet one important and frequently sought-after characteristic of cosmetic compositions is their clarity.
Moreover, said derivatives derived in particular from soy proteins have a relatively high ability to increase viscosity in an aqueous solution, which sometimes makes it difficult to prepare certain compositions, particularly cosmetic compositions, with the aid of such solutions.